Machining features into a cast workpiece is known to be a bottle neck in a mass production facility. One such example of bottleneck in the mass production of a cast workpiece is machining a cast wheel 46 like that shown in FIG. 1. The cast wheel 46 typically includes cut lug nut apertures 60 and a cut valve stem aperture 75, the cutting of which creates a manufacturing bottleneck.
Cast wheels for use on road vehicles are becoming increasingly desirable, particularly when light weight alloys are used to reduce mass. One detriment to increasing market share of cast wheels, in spite of potential mass savings, is the slow manufacturing process when compared to wheels stamped from sheet metal. While the casting process is slow relative to forming sheet metal, a bottleneck in the manufacturing process has been the machine operation, in particular when forming apertures to receive lugs and valve stems. For example, referring to FIG. 2, a prior art spindle machine is generally shown at 10. The current spindle machine 10 includes a fixture 12 onto which a wheel 14 is mounted. A cutting tool 16 is affixed to a spindle 18. The spindle 18 and cutting tool 16 are oriented in a vertical direction along a Z axis of a Cartesian coordinate system.
The spindle 18 moves in a circumferential direction around the fixture 12 as will be further explained below. The fixture 12 rotates around a Y axis, as also will be explained herein further below. In this manner, the cutting tool 16 is moved to a plurality of locations around the wheel 14 to cut desired apertures.
The steps of forming lug apertures 20 in the wheel 14 are represented in FIGS. 2 through 4. As shown in FIG. 2, the wheel 14 is mounted on the fixture 12 in a vertical orientation and the cutting tool 16 is moved to the location of the first lug aperture 20. The spindle 18 moves the cutting tool 16 in a circumferential direction around the Z axis cutting a plurality of lug apertures 20 into a face 24 of the wheel 14. When the wheel is rotated to the orientation shown in FIG. 3, a second cutting tool 26 is affixed to the spindle 18 as identified by TC of FIG. 3 for identifying a Tool Change. At that time, the wheel is rotated around the Y axis so that the rear surface 28 of the wheel faces the cutting tool 16. In FIG. 4, the second cutting tool 26 moves in a circumferential direction around the Z axis for cutting a second configuration into the rear surface 28 of the wheel 14, in this example, a complimentary feature in the aperture 20.
When step of machining the wheel 14 that is shown in FIG. 4 is completed, the wheel 14 is again rotated around the Y axis and an additional tool change TC is performed to affix a third cutting tool 30 to the spindle 18. The fixture 12 again pivots the wheel 14 on the Y axis to position the third cutting tool 30 at the location of the valve stem aperture 22. Once the third cutting tool 30 forms a portion of the valve stem aperture 22, the fixture 12 again rotates the wheel 14 on the Y axis to the orientation shown in FIG. 5 and conducts an additional tool change TC to a fourth cutting tool 32 to cut a rear portion of the valve stem aperture 22. Once completed, another tool change TC is performed and the fixture 12 rotates the wheel to original position at which time the wheel 14 is removed.
It should be understood to those of ordinary skill in the art that four tool changes TC are required and four rotations of the fixture around the Y axis are conducted through steps shown in FIGS. 2 through 5. The cutting process described above has become a bottleneck to the manufacturing process of a cast wheel. It would be desirable to streamline this process to improve efficiency and reduce cycle time to reduce the cost of manufacturing.